A/C Light Blinking How to Confirm Compressor Clutch Engages

So my AC quit suddenly on my 2013 Tacoma with the blinking light. It worked once since it went out and usually just blows warm air. I wasn't too worried about it but have to drive across the country in a week and AC would be nice out in the desert! I have read a common issue is the relay. I have swapped the relay with the horn and the trailer light relays and it still is not working. I thought it may be low on refrigerant and when I connected the gauge it showed around 120 PSI. I read this could be due to the clutch not engaging. When I turn on the AC button the idle picks up but I don't think the clutch is engaging. I read with many vehicles you can look at the middle of the pulley and check if the plastic region is spinning with the pulley when it engages. Is this the same with the Tacomas? It doesn't appear to spinning. If this is the case could it be a bad clutch and can you test the resistance of the coils on the clutch? Can you also check at the clutch if it is getting the voltage needed?

 

Look at these:

www.customtacos.com/tech.old/files/05FSM/data/ileaf/06toyrm/06toypdf/06rmsrc/rm2006ta/04600710.pdf

www.customtacos.com/tech.old/files/05FSM/data/ileaf/06toyrm/06toypdf/06rmsrc/rm2006ta/046007.pdf

www.customtacos.com/tech.old/files/05FSM/data/ileaf/06toyrm/06toypdf/06rmsrc/rm2006ta/046008.pdf

 

For a lucky fix, you might check the pressure sensors, particularly the connectors. If the center of the hub is not spinning, the compressor is not running. There are several possibilities...

(1) low on refrigerant. 120 psi when system is off says you at least have some r134a. But it doesn't say how much. 120psi when ambient air is cool would be a reasonable pressure. Not so much if it is 100 degrees outside.

(2) bad pressure sensors can also interfere.

(3) bad A/C compressor relay (which you have already checked it seems).

(4) bad compressor clutch. The coil can open on occasion and once the wire breaks internally, its done until the clutch is replaced.

(5) the ECU can tell the compressor clutch to disengage. You might see that under heavy acceleration, for example.

(6) there is a sensor (thermistor) in the airbox that tells the ECU that the evap core is getting too cool.

(7) the A/C "amplifier" module can fail also.

(8) and finally, one of the most common failure points in any electrical circuit is the connectors that are hidden everywhere. They can become corroded, they can be partially disconnected, etc.

However, I would suspect a mechanical failure first. IE the clutch itself or one of the pressure switches, if it is not low on r134a.

A starting point would be to watch the compressor hub when the A/C it turned on. Does it spin and then stop? If so the A/C compressor rotation sensor might have failed. If it never spins, that sounds more like low pressure as in low r134a. Gauges can help because you can instantly see whether the compressor comes on or not. If it does, the low pressure side will drop and the high pressure side will jump, even if just for a moment.

You said the idle picks up when you switch the system on, which suggests (to me) that the compressor actually comes on. Since you said it suddenly quit, that could be the result of a leak caused by a road object hitting the condenser or one of the lines...

lots of possibilities, impossible to narrow it down without hands-on.

 

Thanks for all the great info. The center of the hub is not spinning so I will try to check the coil on the compressor and ensure it is getting the 12V. It is just a tight space to try to get access. First maybe I will try adding some refrigerant although I am not sure if it will take when the system is at 120 PSI.

 

Don't add refrigerant not knowing whether it is fully charged or not. I think a full charge is only 22oz. If you go too much beyond that you will reduce cooling, AND increase pressure which can cause leaks particularly in the evap core which is a pain to replace.

One quick test, the tacoma has a dual-function pressure switch on the high-pressure line. Disconnect the connector and while being careful, short the two wires together while the truck is cranked and see if the clutch clicks and the compressor spins. This switch apparently monitors both low and high pressure at the same time, and will supposedly "open" at pressures below something like 28 PSI. Normal pressures are in the 200 PSI range so the high pressure cutoff is probably set up around 250 or perhaps higher.

If the compressor runs, I would undo the short and hook up gauges to make sure that the pressures are within reason. IE 30-50 on low side, maybe 190-220 on high side (these vary with ambient temp and cab temp however). If the pressures are normal, then the switch has failed (if shorting the connector causes the compressor to run. I have not replaced one on my truck, so I can't directly say, but some vehicles I have worked on have a schrader valve which means you can simply remove and replace the switch without discharging the system. Others require that you recover the freon from the system, then replace the switch, then re-charge.

EDIT: A schrader valve between the switch and line. A toyota A/C tech could tell you whether that is the case or not.

The clutch is pretty easy to test. Connect battery + to the clutch terminal and you will hear it "snap" closed. If it does, the clutch itself is OK. If not, it is a pain to replace since it is buried, but you can get it off without discharging the system.

Best diagnostic tool is a set of R134a gauges. You can find 'em at Harbor Freight for around 50-60 bucks. Then you are not proceeding blindly.

 

Everything Robert said is the absolute truth! You would be well advised to follow his lead.

 

Eggzactlee! If the gauge reads 120 psi and doesn't drop when the AC is turned on, you have problems that are not caused by low freon. You may need to take it to a pro.

 

Thanks Robert...I tried shorting the pressure sensor and then turned on the AC and the clutch is not engaging still. I was checking the relay pins to ensure there was power going to the relay and found that two of the pins always had power. For the 4 pin relay I found a schematic showing the pinout below (the lower relay) and Pins 5 and 2 had power (this must not be the correct diagram for the AC relay). Shouldn't only one pin have power and another pin get power when I turn on the AC? Does anyone have a wiring diagram or correct schematic? I would like to try supplying power to the clutch to see if it engages next but I want to be sure which is the correct pin for the clutch (I would assume it would be pin 3). Also the resistance from pin 3 to ground was pretty high around 4kOhms but I am going to retest it with a better fluke meter instead of the harbor freight freebie.

 

Hard to say about your question. There are two sides to the relay, obviously. The battery/load are obvious. But the other side can have 12v on one pole, and the other can go to a transistor that is only turned on when A/C is needed. So you could always have +12v on one side, but nothing on the other and the relay will stay open. You could hook an ohmmeter to the ground side of the relay and the other lead to the frame ground and you will probably see infinite resistance. If you see 0.00 or very close to it, the relay ought to snap closed and you should be able to hear/feel it.

To test the clutch I was talking about going underneath the truck and disconnecting the clutch wire connector and applying 12 volts _there_.

Note, after re-reading, your 4K ohm resistance is probably equivalent of "open" as 12 volts / 4K = 3ma, which is not enough to snap the relay closed. That almost certainly means you are measuring through a transistor that is not switched on by having power applied to its "base".

 

120 psi still could be low 134 but usually the clutch will short cycle. If the error light is on it's generally the compressor is not turning it has a speed sensor.

 

Looks like the magnetic clutch is bad. Checked the resistance and its 20MOhm or so so pretty much an open circuit. 12V goes to it when A/C is on and trying to power it separately I can't hear it engage.

I don't see just the clutch being sold anywhere. Do you have to replace the whole compressor with the clutch?

 

Napa appears to sell one for my 2007 pre runner v6. But it is probably better to call as the online lookup is often wrong or misleading.

the clutch is a bit of a pain to replace on-vehicle as it is pretty crowded and also awkward to work laying on the ground. But I have replaced quite a few (not on a Tacoma yet...).

These things typically go for a hundred bucks or so, but I have, on occasion, found compressors where the clutch was not sold separately for unknown reasons. Next step up is a compressor in the $200-$300 range, not to mention the evacuation and recharge cost.

 

Thanks I just called Napa and they told me I had to buy the whole compressor. Found one on Amazon for $160 though so not bad:

$183 UAC CO 10835C A/C Compressor , grey

https://www.amazon.com/UAC-CO-10835C-C-Compressor/dp/B00JJXIV0U/ref=sr_1_1?s=automotive&ie=UTF8&qid=1471537810&vehicle=2013-76-1037-20--53-9-8-8087--8-1---1-0&sr=1-1&ymm=2013%3Atoyota%3Atacoma&keywords=air+conditioner+compressor

Labor is just going to be pricey since the system has to be evacuated.

I just called the company and they said it fits a 2013 base unit but wasn't listed for the TRD Off-Road. They showed the Tacoma OEM number that this compressor matched was 8832004060. I wouldn't think the base unit would be any different than the TRD version. Can anyone confirm?

 

I just changed my compressor recently and recharged the system myself. There are a few really good videos on YouTube by the user "chrisfixit".

Some words of advice: they shouldn't charge much to evacuate the system because they get to keep the freon and re-use it. If you want to recharge the system yourself, auto zone has the vacuum pump available in their loan-a-tool program. I borrowed the gauge set from a friend, but Amazon has a gauge set for $50. New compressor, 2 cans of refrigerant, can tap, and ac dye all totaled a little less than $400.

**edit...I went for the OEM Delphi AC compressor $330. Comes with 2oz of oil, just need to add a tiny bit of dye

 

Thanks for the tips. Doesn't sound too bad then but I found a shop that could do it around $700. I am wondering by the time I buy that with the gauge set and find somebody here in CA to evacuate the systems it might be worth spending an extra couple hundred to have a shop do it.

 

Especially if you're in a time crunch. I have little trust in my local repair shops though

 

Yeah....you hit the nail on the head with local repair shops....took it in this morning to get it swapped out before leaving. Just got a call that the part he received was the wrong one after tearing everything apart. I would think you would want to confirm that before ripping into everything. Looks like it will be windows down through the desert! I guess at this point since the system has been evacuated then I may as well replace it myself and follow the links you posted.

 

Sometimes you have to take it apart to see if the replacement part is the correct one. Been there done that bit me in the ass too.

 

It's really not too difficult. The outer part of my clutch separated from the inner part...I could have just replaced the clutch, but I've read about a lot of compressors seizing before 10 year mark. If the compressor seizes, it involves a flush of the system and replacing a few other components because of the metal shavings, so I just replaced the whole thing. If your certain that your clutch is what's bad...autozone also has the special tool to remove replace the clutch only, if you wanted.

 

Will probably replace the whole unit as you did especially since the system has been evacuated now. Just trying to make sure parts are compatible before ordering. Found a UAC 10835c compressor for 160 off Amazon and it appears it should fit just need to find the seals (I don't think the 2013 is different). In the video by chrisfixit he shows the seals but unfortunately only one bag that had the following part #90210-A0004. Anyone know the other OEM part number for the seal?